沥青混合料动态模量试验标准研究
Study on test standard of asphalt mixture dynamic modulus

以国外研究成果和经验为基础,采用无侧限抗压测试方法测定沥青混合料的动态模量,对静压成型试件的空隙分布不均匀性进行了验证,对试件制作方法进行了改进,得到了静压成型切割试件,并对2种试件的空隙率进行对比分析。根据Vander Poel公式,确定了荷载频率。采用有间隙的加载模式,以试样达到稳态振动为基本原则确定了荷载循环作用次数,并以最后5次的平均应变峰值计算动态模量。确定了荷载级位与应变测量方式,并选取处于稳定期的试验数据作为最终的试验结果。测试了静压成型切割试件的动态模量,计算了动态模量均值、均方差与变异系数。分析结果表明:静压成型切割试件的空隙率平均为4.2%,远小于静压成型试件的空隙率平均值6.5%,而且离散性较小,试件空隙分布均匀,较静压成型试件更接近马歇尔试件的空隙率,且在荷载作用下更容易达到稳定状态; Haversine荷载波形、10 Hz荷载频率、0.9 s荷载作用间隙时间和0.7 MPa荷载级位较接近行车荷载的作用; 采用顶面法测量试件变形; 当荷载作用次数为200次时,认为试件已达到稳态振动,所以荷载循环作用次数取200次; 对于单个试件,选取第3～5次的试验数据计算其动态模量,如第5次与第3次试验动态模量差值大于等于200 MPa,应将试件废弃; 3种沥青混合料动态模量为1 650～2 970 MPa,试验结果离散性较小,均方差为100～230 MPa,变异系数为5%～9%,可见,试验方法可行。
Based on the foreign research achievements and experience, the dynamic modulus of asphalt mixture was measured by using unconfined compressive strength test method. The uneven distributions of static pressing specimens were verified, the making method of specimens was improved, and the cutting static pressing specimens were obtained. The porosities of 2 kinds of specimens were compared. According to Vander Poel formulas, load frequency was determined. The clearance loading mode was used, and the load cycle was determined based on the principle of specimens reaching steady vibration state. Dynamic modulus was calculated according to the average peak strains of last 5 load cycles. The load levels and strain measurement methods were determined, and the test data at stable phase were selected as the final test results. The dynamic moduli of cutting static pressing specimens were tested, and the mean value, mean square deviation and variation coefficient of dynamic moduli were calculated. Analysis result indicates that the average porosity of cutting static pressing specimens is 4.2%, and is far less than the average porosity of static pressing specimens, which is 6.5%. The discrete of cutting static pressing specimens is small, and the void distribution is uniform. Compared with static pressing specimens, the porosities of cutting specimens are closer to Marshall specimens, and the cutting specimens are easier to reach steady vibration state under loading. Haversine wave, load frequency of 10 Hz, load clearance time of 0.9 s and load level of 0.7 MPa are closer to the roles of traffic loads. The top surface method is used to measure the deformation of specimens. The specimens have reached steady vibration state when the load cycles is 200 times, so the load cycles is determined as 200 times. For a single specimen, the test data of 3-5 load cycles are selected to calculate dynamic modulus. When the difference between the dynamic modulus of 3 and